THE TECTONIC AND GEOCHEMICAL MECHANISM OF THE FORMATION OF SOME SYNGENETIC ORE DEPOSITS
Zhao Lunshan Shen Yongli Liu wenhua Zhan weiguo ( Wuhan College of Geology, Wuhan 430074 )
In the reduced sea-bottom water, the reduction of sulfate caused by anaerobic bacteria, which provide S2- as a precipitator, controls the formation of syngenetic sulfide facies. Insufficient compensation state of the subsidense-deposit balance caused by paleotectonic movement in the basin is a favourable condition for the concentration of sulfide minerals. In this case the sulfide ore layers are not diluted by barrep sediments. Geological and geochemical data from some strata-bound ore deposits demonstrate that the subtidal bay and lagoon facies in the epicontinental depression belt make up a "geochemical trap" , where ore-forming metallic elements from continents can be concentrated to form ore deposits with no additional sources required.